So, Ports&Pins - the PWM output for the spindle is on this page, under the "Step Pin" column (and to the right the Step Port). This appears to be set to the same as the active Axis A - which gives me pause to think that the pin settings are wrong. First I'd disabled Axis A, unless you have a 4th axis on the router. At least then there's no conflict.

The next point is to try to find which of the output pins are mapped to the PWM output on the control board. The possible output pins on a parallel port - and I know you have a USB interface but these often mimic the parallel port for compatibility reasons - anyway, possible output pins for a parallel port are:

1 - ?
2 - X Step
3 - Y Step
4 - Z Step
5 - A Step - also Spindle Step (PWM)
6 - X Dir
7 - Y Dir - also Spindle Dir (unused function)
8 - Z Dir
9 - A Dir
10 - ?
14 - ?
16 - ?
17 - ?

On the Spindle page - you have the M3/M4 relays set to Output #1, I can't see in the images above the Pins/Ports for Output #1 - if you can screen shot that? We're trying to find/set the pin to control the spindle on/off...

You've not answered the question as to where the single red wire went to - I'm expecting to the control board - if so, is there any printing on the board that could match the PIN numbers above? If there's no indication then there's a limit to the possible options - as above. I think you should be able to toggle the FOR LED on the VFD controller with M3/M5 on the MDI if you configure OUTPUT #1 with the correct pin number.

That'll leave the PWM pin - we'll save that for later (the wife's getting narky).